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김효상(Hyo-Sang Kim),김대현(Dae-Hyun Kim),안효석(Hyo-Sok Ahn),한준희(Junhee Hahn),이우(Lee Woo) 한국트라이볼로지학회 2009 한국트라이볼로지학회 학술대회 Vol.2009 No.11
Tribological properties of nanoporous structured alumina film was investigated. Alumina film (AAO: anodic aluminum oxide) of 2 ㎛ thickness having nanopores of 45 ㎚ diameter with 105 ㎚ interpore-diatance was fabricated by mild anodization process. Reciprocating ball-on-flat sliding friction tests using 1 ㎜ diameter steel ball as a counterpart were carried out with wide range of normal load from 1 mN to 1 N in an ambient environment. The morphology of worn surfaces were analyzed using scanning electron microscopy. The friction coefficient was strongly influenced by the applied normal load. Smooth layer patches were formed on the worn surface of both AAO and steel ball at relatively high load (100 mN and 1 N) due to tribochemical reaction and compaction of wear debris. These tribolayers contributed to the lower friction at high loads. Extremely thin layer patches, due to mild plastic deformation of surface layer, were sparsely distributed on the worn surface of AAO at low loads (1 mN and 10 mN) without the evidence of tribochemical reaction. Delaminated wear particles were generated at high loads by fatigue due to repeated loading and sliding.
김효상(Hyo-Sang Kim),김대현(Dae-Hyun Kim),안효석(Hyo-Sok Ahn),한준희(Junhee Hahn),이우(Lee Woo) 한국트라이볼로지학회 2010 한국윤활학회지(윤활학회지) Vol.26 No.1
Tribological properties of nanoporous structured alumina film was investigated. Alumina film (AAO: anodic aluminum oxide) of 60 μm thickness having nanopores of 45 nm diameter with 105 nm interpore-diatance was fabricated by mild anodization process. Reciprocating ball-on-flat sliding friction tests using 1 mm diameter steel ball as a counterpart were carried out with wide range of normal load from 1 mN to 1 N in an ambient environment. The morphology of worn surfaces were analyzed using scanning electron microscopy. The friction coefficient was strongly influenced by the applied normal load. Smooth layer patches were formed on the worn surface of both AAO and steel ball at relatively high load (100 mN and 1 N) due to tribochemical reaction and compaction of wear debris. These tribolayers contributed to the lower friction at high loads. Extremely thin layer patches, due to mild plastic deformation of surface layer, were sparsely distributed on the worn surface of AAO at low loads (1 mN and 10 mN) without the evidence of tribochemical reaction. Delaminated wear particles were generated at high loads by fatigue due to repeated loading and sliding.
김대현(Dae-Hyun Kim),김민석(Min-seok Kim),한준희(Junhee Hahn),안효석(Hyo-Sok Ahn) 한국트라이볼로지학회 2012 한국윤활학회지(윤활학회지) Vol.28 No.5
A modified thermal noise method was proposed to measure the normal spring constants of the colloidal probes for an atomic force microscope. We used commercial tipless cantilevers (length 150, width 30, nominal k 7.4 N/m) and borosilicate spheres with a diameter of 20 to fabricate colloidal probes. The inverse optical lever sensitivity of both the tipless cantilever and colloidal probes were used to measure the normal spring constant of the colloidal probes. We confirmed the accuracy and usefulness of our method by comparing the measurement results with those obtained using the nanoforce calibrator (NFC), which reportedly has an uncertainty of 1.00%. The modified thermal method showed a good agreement (~10% difference) with the NFC, allowing us to conclude that the modified thermal method could be employed for the effective measurement of the normal spring constants of colloidal probes.
접촉 공진 힘 현미경 기술을 이용한 플립 칩 범프 재료의 국부 탄성계수 측정
김대현(Dae-Hyun Kim),안효석(Hyo-Sok Ahn),한준희(Junhee Hahn) 한국트라이볼로지학회 2012 한국윤활학회지(윤활학회지) Vol.28 No.4
We used contact resonance force microscopy (CRFM) technique to determine the quantitative elastic properties of multiple materials integrated on the sub micrometer scale. The CRFM approach measures the frequencies of an AFM cantilever’ first two flexural resonances while in contact with a material. The plain strain modulus of an unknown or test material can be obtained by comparing the resonant spectrum of the test material to that of a reference material. In this study we examined the following bumping materials for flip chip by using copper electrode as a reference material: NiP, Solder (Sn-Au-Cu alloy) and under filled epoxy. Data were analyzed by conventional beam dynamics and contact dynamics. The results showed a good agreement (~15% difference) with corresponding values determined by nanoindentaion. These results provide insight into the use of CRFM methods to attain reliable and accurate measurements of elastic properties of materials on the nanoscale.
김효상(Hyo-Sang Kim),김대현(Dae-Hyun Kim),한준희(Junhee Hahn),안효석(Hyo-Sok Ahn) 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.4
Friction behavior of nanoporous anodic aluminum oxide(AAO) film was investigated. A 60 μm thick AAO film having nanopores of 45 nm diameter with 105 nm interpore-diatance was fabricated by mild anodization process. The AAO film was then saturated with paraffinic oil. Reciprocating ball-on-flat sliding friction tests using 1 mm diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 N to 1 N in an ambient environment. The morphology of worn surfaces were analyzed using scanning electron microscopy. The friction coefficient significantly increased with the increase of load. The boundary lubrication layer of paraffinic oil contributed to the lower friction at relatively low load (0.1 N), but it is less effective at high load (1 N). Plastic deformed layer patches were formed on the worn surface of oil-enriched AAO at relatively low load (0.1 N) without evidence of tribochemical reaction. On the other hand, thick tribolayers were formed on the worn surface of both oil-enriched a nd as-prepared AAO at relatively high load (1 N) due to tribochemical reaction and material transfer.
송근동(Geun Dong Song),황정호(Jeong Ho Hwang),김대웅(Dae-Woong Kim),허용학(Yong-Hak Huh),정인현(In Hyun Cheong),홍성구(Seong-Gu Hong),한준희(Junhee Hahn) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
Super304H is a promising candidate for heat exchangers in boiler systems used in thermal power plants operating at ultra-supercritical conditions, and the mechanical properties of its weld play a decisive role in the reliability of the thermal power plant. Herein, we report the fatigue properties of Super304H weld at 600 ℃, focusing on the operating temperature in the field. Our results showed a drastic reduction in the fatigue resistance was observed in the weld at low strain amplitudes (< ~0.3%), which was associated with the transition of the fatigue failure location (mechanism) from the base metal to the weld metal. This coexistence of two distinct fatigue failure mechanism in Super304H weld is discussed in relation to the microstructural evolution of weld metal with thermal aging times.